JPH09186060A - Charged particle beam exposure system - Google Patents

Abstract

(57) [Abstract] [Problem] To improve the turnaround of an exposure apparatus by detecting a trouble of a stage moving mechanism by using an existing function of measuring rotational displacement of a stage around multiple axes and eliminating unnecessary cause investigation. . A charged particle beam source, a converging unit for converging a charged particle beam from the source, a deflecting unit for deflecting the charged particle beam converged by the converging unit, and a deflector for deflecting the deflected unit. A stage on which a sample to be exposed with a charged particle beam is placed, a measuring means for measuring the rotational displacement of the stage around multiple axes, and a rate of change of the value measured by the measuring means (or an absolute value or on a time axis). Change amount) exceeds a reference value, the determination means determines an abnormality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention irradiates a substrate or a thin film (hereinafter referred to as a "sample") coated with a resist that absorbs and reacts with a beam of charged particles such as electrons and ions, to the desired beam. The present invention relates to an improvement of a charged particle beam exposure apparatus that exposes a fine pattern.

[0002]

2. Description of the Related Art Conventionally, when a desired fine pattern is formed on a sample by a charged particle beam, in order to correct the positional deviation of the charged particle beam, an XY laser length measuring device is used to measure a sample table (hereinafter referred to as "stage"). The X-direction displacement and the Y-direction displacement of (i.e.) are measured, and the deflection angle corresponding to the displacement amount is given to the charged particle beam. However, the error of so-called Abbe cannot be corrected by only that. Various measures were taken.

First, the error of Abbe will be outlined. In FIG. 13, the measurement point by the XY laser length measuring device is the stage 1
Is an intersection point P of two lines passing through points x and y on the XY end surface of
A point P is a virtual point located inside the stage 1. Although not shown, the sample is placed on the surface of the stage 1 and the point Q on the sample is irradiated with the charged particle beam 2, so the point Q is always located above the point P. Assuming that the stage 1 is inclined by an angle δ as shown by a broken line 3, the line connecting the points Q and P is also inclined by the same angle δ,
Will move to point Q '. As a result, since the charged particle beam 2 is irradiated on the point Q, an error (Abbe's error) corresponding to the distance between the points Q and Q'is produced.

In order to correct the Abbe's error, it is essential to measure the angle δ. The amount of error (distance between points Q and Q ') is
This is because the distance between the points P and Q can be calculated by multiplying the angle δ. For example, the distance between points P and Q is 3 mm, and the angle δ is 10
^{At −5} degrees, the Abbe error is 0.03 μm.
The error may be canceled by shifting the electron beam irradiation point by 0.03 μm.

Abbe errors actually occur in combination with the rotational displacement of the stage 1 around multiple axes. FIG.
FIG. 4 is a schematic configuration diagram of a main part of a conventional charged particle beam exposure apparatus, where 4 is a sample (for example, a semiconductor wafer) placed on a stage (not shown), and 5 is L along an XY coordinate axis parallel to the surface of the sample 4. Mirrors arranged in a letter shape, 6 is a first interferometer that optically measures the displacement of one surface 5a of the mirror 5, and 7 is a second interferometer that optically measures the displacement of the other surface 5b of the mirror 5. An interferometer, 8 is a beam splitter for distributing a laser beam 9 from a light source (not shown) to the first interferometer 6 and the second interferometer 7.

The first interferometer 6 has a value (L) corresponding to ½ of the base length of an inverted isosceles triangle (see FIG. 14B) virtually set on the one surface 5a of the mirror 5.
1) and the value (L2) corresponding to the height, and the value (Y) corresponding to the distance to one end of the base of the same triangle.
1) and the value corresponding to the distance to the vertex of the same triangle (Y
2), and the second interferometer 7 has a value (L) corresponding to ½ of the base length of the inverted isosceles triangle virtually set on the other surface 5b of the mirror 5.
1) and a value (L2) corresponding to the height, and a value (X
1), a value (X3) corresponding to the distance to the other end of the base and a value (X2) corresponding to the distance to the apex of the same triangle are measured.

If the following equations (1) to (3) are calculated using these measured values, the inclination of the stage 1 around the multiple axes can be measured. θ = (X3-X1) / 2 · L1 [rad] ……… ψ = {X2- (X1 + X3) / 2} / L2 [rad] ……… φ = {Y2-Y1- (X3-X1) ・ L2 / 2 · L1} / L2 [rad] ……… where θ is yawing, ψ is rolling, and φ is pitching. For convenience, the sample 4 is regarded as an airplane (see the picture on the sample 4). , Θ corresponds to the rotational displacement of the body about the center of gravity, ψ corresponds to the rotational displacement of the body about the front-rear axis, and φ corresponds to the rotational displacement of the body about the left-right axis.

[0008]

By the way, the conventional charged particle beam exposure apparatus described above can correct the Abbe error by measuring the yawing, rolling and pitching of the stage (that is, the rotational displacement of the stage around multiple axes). This is useful in terms of points, but since it is only a correction technique, the correction limit will not be exceeded if, for example, some trouble occurs in the stage moving mechanism (such as dust on the rails, rail breakage or bending). As far as it goes, there is an inconvenience that the trouble occurrence cannot be known outside. Moreover, even if the correction limit is exceeded, the symptoms of poor exposure simply appear in the table, so various investigations and investigations are necessary to identify the above-mentioned troubles, and the problem of worsening the turnaround of the exposure apparatus. There was a point.

Therefore, according to the present invention, the existing function of measuring the rotational displacement of the stage about multiple axes is used to detect the trouble of the stage moving mechanism, thereby eliminating the needless investigation of the cause and thereby the turnaround of the exposure apparatus. The purpose is to improve.

[0010]

In order to achieve the above object, the present invention has a charged particle beam generation source, a converging means for converging a charged particle beam from the source, and a converging means. Deflection means for deflecting the charged particle beam, stage for placing a sample exposed by the charged particle beam deflected by the deflection means, measuring means for measuring rotational displacement of the stage around multiple axes, and the measurement And a determination unit that determines an abnormality when the rate of change of the value measured by the unit (or the absolute value or the amount of change on the time axis) exceeds a reference value.

When the rotational displacement around the multi-axis of the stage suddenly increases (increased rate of change), for example, a trouble such as adhesion of dust on the rail of the stage moving mechanism or chipping of the rail occurs, and When the rotational displacement becomes large on average (increase in absolute value), for example, a trouble such as bending of the rail of the stage moving mechanism occurs, and further, a certain time in the past and the current time If the same rotational displacement is different between the two, for example, when some trouble occurs in the stage moving mechanism within that time,
According to the present invention, it is possible to immediately warn of the occurrence of a trouble related to the rotational displacement of the stage around multiple axes, and it is possible to improve the turnaround of the exposure apparatus without needless investigation of the cause.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 11 are views showing an embodiment of a charged particle beam exposure apparatus according to the present invention. First, the configuration will be described. In FIG. 1, the exposure control apparatus 10 includes a central processing unit 11, a storage unit 12, and a bus 13, and
Buffer memory 14, data management unit 15, exposure management unit 1
6. Deflection amount setting unit 17 for main deflector, deflection amount setting unit 18 for sub deflector (pattern generation unit 18a, pattern correction unit 18)
b, clock setting unit 18c), mask stage control unit 1
9, a blanking control unit 20, amplifier units 21 to 26, an Abbe error correction amount generation unit 27, an Abbe error correction unit 28, a stage control unit 29, a laser measurement unit 30, a stage drive mechanism 31, and the like.

FIG. 2 is a schematic block diagram of the exposure apparatus main body controlled by the exposure control apparatus 10.
Is a charged particle beam source 44 having a cathode electrode 41, a grid electrode 42 and an anode electrode 43, and a charged particle beam generated by the charged particle beam source 44 (hereinafter,
(Hereinafter, simply referred to as “beam”), for example, a first slit 45 for forming a rectangular cross section, a first lens 46 as a converging unit for converging the formed beam, and a beam according to the correction deflection signal AS1. Slit deflector (deflecting means) 47 for correcting and deflecting, second and third lenses 48 and 49 arranged to face each other, and the second and third lenses 48 and 4
Stencil mask 50 (K1 is a schematic representation of control operation force for movement) mounted so as to be movable horizontally (left and right in the drawing) between 9 and both sides (in the drawing). The second and third lenses 4 are arranged on the upper and lower sides, respectively, according to the position data signals AP1 to AP4.
Beams 8 and 49 are deflected to select one of a plurality of transmission holes (not shown) on the stencil mask 50.
Deflectors (deflecting means) 51 to 54, a blanking gate 55 for blocking or passing a beam in response to a blanking signal ABLK, a third lens 56, an aperture 57, a refocusing coil 58, 4th lens 5
9, focus coil 60, and stig coil 61
And the fifth lens 62 and the exposure position determination signals AS2, A
A main differential coil 63 and a sub deflector (deflecting means) 64 for positioning the beam on the wafer W according to S3.
A stage 65 on which a wafer W as a sample is placed and movable in XY directions, first to fourth alignment coils 66 to 69, and a mirror 7 attached to the stage 65.
0 (the same as the mirror 5 in FIG. 14). LS is a laser beam, AS4 is a signal for controlling the focus of the beam, and K2 is a stage 65.
It is a schematic representation of the control operation force of.

FIG. 3 is an external view of the stage 65. The stage 65 has a base member 71 firmly fixed to a floor or the like, and a rail 72 in the X direction and a rail 73 in the Y direction are attached to the base member 71 in a cross shape. The rail 72 in the X direction and the rail 73 in the Y direction are
Pulley mechanism parts 74 and 75 are attached,
These pulley mechanism parts 74 and 75 are used for the rail 72 in the X direction.
And along the Y direction rail 73, and also along the X direction rail 77 and Y direction rail 78 fixed to the lower surface of the stage upper plate 76. Although not visible in the figure, the rails 72, 73 on the base member 71 side and the rails 77, 78 on the stage upper plate 76 side cross each other in a cross shape and are divided into two at the intersection. There is. In addition, a plurality of pulley mechanism parts (actually four) 74 and 75 which can be seen only two are a plurality of which are active along the rails 72 and 73 on the base member 71 side and the rails 77 and 78 on the stage upper plate 76 side. For example, when the rails 73 and 77 in the Y direction are described as a representative, as shown in FIG.
The direction rail 73 has four wheels 73a to 73d that operate along the side surfaces of the rail 73 and one wheel 73e that operates along the upper surface of the rail 73,
Similarly, the rail 77 in the Y direction on the stage upper plate 76 side is
Four wheels 77a that run along the sides of the rail 77
It has 73d and one wheel 77e which operates along the lower surface of the rail 77.

"Exposure processing" applied to such a configuration
And a schematic flowchart including "a trouble determination process of the stage moving mechanism" are shown in FIG. Step 80 is a charged particle beam alignment process, and step 81 is an exposure process, which are conventionally performed processes. These conventional steps 80 and 81 are repeatedly executed until the preset adjustment period is reached. When the predetermined adjustment period is reached, the yawing θ, rolling ψ, and pitching φ of the stage 65 are measured in step 83 (measuring means) in order to confirm the occurrence of Abbe error. The Abbe error correction amount generator 27 of FIG. 1 is for that purpose. In the figure, the measured value of yawing θ is Y
i, the measured value of rolling ψ is Ri, and the measured value of pitching φ is Pi. i is the rails 73 and 78 in the Y direction
And numbers of measurement points provided at equal intervals or along the X-direction rails 72 and 77 (see FIGS. 6 and 7).

The following steps 84 to 86 (determining means)
Is a measurement value evaluation routine that is a feature of this embodiment. In step 84, the measured value Pi (absolute value) of the pitching φ is compared with the reference value α, and if it exceeds the reference value α, it is determined that there is a trouble (evaluation result NG). In step 85, the change rate (absolute value) of the measured value Pi of the pitching φ is compared with the reference value β, and if it exceeds the reference value β, it is determined that there is a trouble (evaluation result NG). In step 86, the difference value (absolute value) of the measured value Pi of the pitching φ on the time axis is compared with the reference value γ, and if it exceeds the reference value γ, it is determined that there is a trouble (evaluation result NG). . The evaluation formulas in steps 84 to 86 are as follows. (Step 84) | Pi | <α ... (Step 85) (| Pi-Pi _-1 |) / L <β ... (Step 86) | Pi-Pi '| <γ ... However, Pi _-1 : Pi at the measurement point immediately before Pi L: measurement unit length Pi ': Pi before the measurement cycle, If NG is determined in these steps 84 to 86, some trouble in the stage moving mechanism, for example, the stage Trouble with yawing, rolling, and pitching (that is, rotational displacement of the stage around multiple axes) has occurred. As a typical example of trouble, when NG is determined in step 84, the rail may be locally deformed, chipped, or dust may be attached. Alternatively, when NG is determined in step 85, the rail may be entirely deformed, distorted, or displaced from the mounting position. Alternatively, when NG is determined in step 86, various troubles that may occur between the previous measurement and the current measurement are conceivable.

FIG. 8 is a diagram showing an example of a trouble.
Here, the dust adhering to the rail and the loss of the rail are shown. For example, dust on the rails causes the pitching of the stage to change, as shown in FIG. FIG. 10 is a diagram showing an example of the measurement result. The vertical axis is the measured value,
The horizontal axis represents the position on the rail, the solid line represents rolling ψ, the alternate long and short dash line represents pitching φ, and the dotted line represents yawing θ. When the adjustment of the stage moving mechanism is completely ideal, the solid line, the dash-dotted line, and the dotted line should always change with a constant measurement value regardless of the change in the position. Due to various factors such as loss or bending of the rail, it shows a unique change tendency. For example, when dust adheres to the rail, an instantaneous rise (see reference numeral a) occurs on the solid line (rolling) and the alternate long and short dash line (pitching) at the adhesion position, or the entire rail is curved. In this case, since the dotted line (yawing) curves along the curve, the cause can be specified by detecting these peculiar tendencies.

For example, in the case of FIG. 10, a certain time (t
x) shows a peculiar tendency that the alternate long and short dash line (pitching) rises abruptly, so the measured value P before and after tx
As the difference of i increases, the absolute value of the measured value Pi immediately after tx increases, and the rate of change of the measured value Pi immediately after tx also increases rapidly. Therefore, the reference values α, β, γ
If the optimum setting is made, the peculiar tendency can be detected by the above-mentioned steps 84 to 86, and an alarm or the like can be issued to prompt maintenance of the stage moving mechanism.

FIG. 11 shows the measurement results after the maintenance (rail cleaning) is performed, and as can be seen from the figure, the rapid rising is removed from the solid line (rolling) and the alternate long and short dash line (pitching). As described above, in this embodiment, the pitching of the stage is measured along the X and Y directions at equal intervals or at appropriate intervals, and the unique change tendency of the measured value is detected to determine the trouble of the stage moving mechanism. Therefore, it is possible to take necessary measures (for example, rail cleaning) immediately upon occurrence of a trouble, and it is possible to improve turnaround of the exposure apparatus without needless investigation of the cause.

In the above embodiment, the trouble is judged based on the pitching, but it is not limited to this. You can also add rolling and yawing. Further, it is preferable to store the exposure position of the wafer at the time of trouble determination and refer to the stored information at the time of chip inspection after the completion of the exposure processing because the inspection time can be shortened.

As shown in FIG. 12, the measurement of the first interferometer 6 is set to Y1 to Y3, and a new measuring means for measuring the changes Z1 and Z2 of the Z axis of the mirror 5 (shown in the figure). Is omitted, but if a laser length measuring device) is provided,
Problems such as a mounting error of the mirror 5 and a shift due to vibration can also be determined. Y3 can be represented as Y3 = Y1 + (X1-X3) ... Using X1, X2, X3, Y1, and Y2, and similarly (Z2-Z1) is (Z2-Z1) = ( L3 / L2) · {X2- (X1 + X3) / 2} ... And the ideal value of Y3 or (Z2-Z1) can be calculated from X1, X2, X3, Y1, and Y2. The difference between this ideal value and the actual measured value is obtained, and when the difference exceeds a certain value, the occurrence of trouble can be determined.

[0022]

According to the present invention, the existing function of measuring the rotational displacement of the stage about multiple axes is used to detect the trouble of the stage moving mechanism. Therefore, it is possible to obtain the advantageous effect that the prior art does not have, that is, it is possible to improve the turnaround of the exposure apparatus without needless investigation of the cause.

[Brief description of the drawings]

FIG. 1 is a block diagram of an exposure control unit according to an embodiment.

FIG. 2 is a configuration diagram of an exposure unit according to an embodiment.

FIG. 3 is a configuration diagram of a stage according to an embodiment.

FIG. 4 is a configuration diagram around a rail according to an embodiment.

FIG. 5 is a flowchart of a main part of the embodiment.

FIG. 6 is a stage movement diagram for measurement according to an embodiment.

FIG. 7 is a measurement point diagram of an example.

FIG. 8 is a trouble diagram of an example.

FIG. 9 is a trouble diagram with a pitching change according to an embodiment.

FIG. 10 is a graph showing the measurement results of one example.

FIG. 11 is a graph showing measurement results after performing necessary treatments in one example.

FIG. 12 is another improved configuration diagram of the embodiment.

FIG. 13 is an explanatory diagram of an Abbe error.

FIG. 14 is a diagram showing an Abbe error measurement system.

[Explanation of symbols]

 W: Wafer (sample) 44: Charged particle beam generation source 46: First lens (converging means) 47: Slit deflector (deflecting means) 51 to 54: First to fourth deflectors (deflecting means) 63: Main Differential coil (deflecting means) 64 Sub deflector (deflecting means) 65: Stage 83: Step (measuring means) 84 to 86: Step (determining means)

Continuation of the front page (72) Toru Ikeda Tohru Ikeda 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Yoshihisa Ohba, 1015 Kamedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture (72) Invention Person Akio Yamada 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (3)

[Claims] 1. A charged particle beam generation source, a converging means for converging a charged particle beam from the generation source, and a deflecting means for deflecting the charged particle beam converged by the converging means.
A stage on which a sample to be exposed by the charged particle beam deflected by the deflecting means is placed, a measuring means for measuring the rotational displacement of the stage around multiple axes, and a rate of change of the value measured by the measuring means are A charged particle beam exposure apparatus, comprising: a determination unit that determines an abnormality when a reference value is exceeded. 2. A charged particle beam generation source, a converging means for converging the charged particle beam from the generation source, and a deflecting means for deflecting the charged particle beam converged by the converging means.
A stage on which a sample to be exposed by the charged particle beam deflected by the deflecting means is placed, a measuring means for measuring rotational displacement of the stage around multiple axes, and an absolute value of a value measured by the measuring means is A charged particle beam exposure apparatus, comprising: a determination unit that determines an abnormality when a reference value is exceeded. 3. A charged particle beam generating source, a converging means for converging the charged particle beam from the generating source, and a deflecting means for deflecting the charged particle beam converged by the converging means.
A stage on which a sample to be exposed by the charged particle beam deflected by the deflecting means is placed, a measuring means for measuring the rotational displacement of the stage around multiple axes, and a time axis of the value measured by the measuring means. A charged particle beam exposure apparatus, comprising: a determination unit that determines an abnormality when the amount of change in the value exceeds a reference value.